1. Technical Field
The present disclosure relates generally to the field of pathogen reduction in food processing media, and more particularly to the use of inorganic chloramines as antimicrobial agents in food processing waters used upon food products.
2. Background of the Related Art
Potable water treatment facilities have two primary objectives in controlling pathogens in the public drinking water supply. The first is to eliminate pathogens as part of the water treatment process within the treatment plant and the second is to provide a residual disinfectant in the finished water to prevent microbial regeneration in the distribution system that carries the water to the consumer.
Because of its efficacy in inactivating a wide range of microbes, chlorination became the standard method for disinfecting potable water in both the water treatment plant and in the distribution system.
However, the reaction of chlorine with naturally occurring organic matter (NOM) in the water can result in the formation of suspected carcinogens such as chloroform, which is in the group of potentially dangerous disinfection byproducts called trihalomethanes. Growing public health concerns gave rise to the Safe Drinking Water Act Amendments of 1996, which required the U.S. Environmental Protection Agency (EPA) to develop new drinking water regulations, including rules to address simultaneous compliance of microbial disinfection and disinfection by product generation.
The Disinfection and Disinfection By-products Rules established microbial reduction standards, maximum residual levels for disinfectants and limits for disinfection byproducts such as trihalomethanes (THMs) and haloacetic acids (HAA5). Since these byproducts are formed by chlorinating certain organic compounds that are typically present in source waters, many drinking water plants were forced to change their methods of disinfection to reduce the formation of these byproducts.
Because of its chemical characteristics, monochloramine, a slow-reacting and persistent anti-microbial agent that is not prone to react with organic matter, gained widespread use in programs designed to meet the new rules. This chlorine species is generated by the controlled mixing of chlorine and ammonia in water. Currently monochloramine is used primarily to provide a residual biocide in potable water distribution systems. Because of its relatively low antimicrobial efficacy, monochloramine is not generally used as a primary disinfectant in potable water treatment. The increased usage of monochloramine treatment by municipal water treatment facilities is not because of its disinfection qualities, but rather the change is taking place as part of a strategy to avoid production of THMs in drinking water.
In his 1967 work, “Aspects of the Quantitative Assessment of Germicidal Efficiency,” J. C. Morris presented a tabulation of the concentrations of various germicides required to inactivate 99 percent of the targeted microbes in ten minutes of contact time. Today this is called specific lethality and is commonly used to compare the biocidal efficacies of chemical oxidizers. At 5.degree. C., the specific lethality of hypochlorous acid (the active agent in typical chlorination process) was-determined to be at least 200 times that of monochloramine in inactivating enteric bacteria and viruses. Even the hypochlorite ion (the less biocidal component of free chlorine) was determined to have a specific lethality twice that of monochloramine in inactivating enteric bacteria and four times that of monochloramine in inactivating viruses.
Because of their low specific lethalities, chloramines have been generally disregarded in the search for highly efficacious biocides in the food processing industry. Instead, traditional disinfectants (e.g., chlorine) that have been used and proven in potable water treatment have generally been adopted for use within food processing.
When an aqueous medium is used as the vehicle to deliver an antimicrobial agent to a food product during processing, the environment in which the antimicrobial agent must perform is significantly different from that of potable water. In typical potable water the total organic load is a small fraction of what is found in organically laden process water in a food processing plant. Although the effect of the environment (i.e., organic load in the water) on the efficacy of an antimicrobial agent may have been recognized, there seems to have been an underlying assumption by those skilled in the art that the relative efficacies of the various disinfectants would remain the same in process water with a high organic load as compared to potable water. This may partially explain the absence of research and general information on the use of what are traditionally considered “weak disinfectants”, such as chloramines, in applications that require antimicrobial action in food process waters, on food products, and in ice that will contact food products.
One example of food process waters that undergo substantial changes during processing that have a marked effect on the efficacy of added antimicrobial agents can be found in a poultry processing plant. Process water in a poultry processing plant can have extremely high levels of total organic carbon (TOC) and a correspondingly high chemical oxygen demand (COD). Undesirably, any free chlorine added to these high-demand waters rapidly reacts with the organic constituents and is consumed in seconds, becoming unavailable for disinfection. Monochloramine, which is less reactive and more persistent, remains available to inactivate the microbial population and therefore, under these conditions can be a more effective disinfectant than free chlorine. It has been found that monochloramine treated process waters produce a nominal one log (10 fold) reduction in pathogen levels over those treated with equivalent concentrations of sodium hypochlorite (free chlorine). In organically laden water, chloramine disinfection is a more effective disinfecting agent than free chlorine.
A typical poultry processing plant receives live animals from the grow-out farms, slaughters the animals, drains the blood and then removes the feathers, “paws,” heads and detritus in the initial stages of processing. The carcasses are then sent to mechanized evisceration where the internal organs, digestive tract and other edible and inedible parts are removed. In typical operations, some of the internal organs (i.e., heart, liver and gizzards) are harvested for food products. The carcasses are thereafter sent by way of mechanized line operations through a series of washing and sanitizing steps before the product is shipped as “fresh” product, packaged for freezing or further processed. These line operations typically consume large quantities of water, the characteristics of which change substantially during the process as organic matter enters the water.
Accordingly, the poultry processing industry has generally been characterized as a large volume consumer of water in conducting the slaughter, processing and packing of animals for both human consumption and other uses. Recent initiatives by the United States Department of Agriculture (USDA), under the jurisdiction of the Food Safety Inspection Service (FSIS), have resulted in a further increase in the volume of water used to wash poultry carcasses to meet the more stringent requirements of “zero tolerance” for visual fecal contamination.
In addition, poultry industry interests have been actively seeking methods of reducing the consumption of water due to economic reasons and, additionally in some cases, because of limited availability of sufficient volumes of water to meet the processing requirements. Still other considerations involving limited water treatment resources have raised the need to reduce water consumption. One illustrative embodiment of the present invention provides additional solutions to reuse process water and therefore to reducing the volume of water required for processing poultry or other foodstuffs.
Prior food processes have not focused on the need to conserve water from an economic perspective and accordingly, while they may generally involve water reuse applications, their approaches have failed to address critical economic restrictions inherent in poultry and other food processing operations. It is yet another object of the present invention to provide water reuse processes which are economically feasible and which provide improved savings to the food processing manufacturer.
Typical of prior approaches have been efforts directed to the recovery, treatment and recycling of poultry chiller bath water in a closed loop and “semi-closed loop” type of process where water from the chiller baths is treated to remove solids, fats, oil, grease, organic compounds and microorganisms before reintroducing the treated water to the chiller baths. These efforts may be characterized as primarily aimed at reducing the electrical power requirements and thereby costs associated with chilling the water used in these systems of processing operations. These goals are generally met by reusing the already cooled chiller water and trying to reintroduce the already chilled water back into the chiller makeup feed water, thereby reducing the temperature of incoming fresh water. Unfortunately, the recovery of used chiller bath process water brings with it a very high contamination burden requiring extensive treatment. Representative examples of such approaches have been described in U.S. Pat. Nos. 5,728,305; 5,173,190; 5,178,755; 5,053,140; 4,790,943; and 5,593,598. Unfortunately, such approaches have had some limited success in addressing the treatment challenges, they have to date proven to be of questionable economic value to the industry. It is still another object of the present invention to address such deficiencies within the prior art with the use of monochloramine chemistry as well as other approaches and devices, which are economically sensitive.
Prior efforts have also generated a substantial number of devices designed to provide some filtering efforts. U.S. Pat. Nos. 5,759,415; 5,248,439; 5,132,010; 4,876,004; 4,844,189; 4,481,080 and 3,912,533 provide representative examples of such devices. As will be readily noted, some are structurally complex requiring substantial capital expenses and others, while simpler in structure, are aimed at solving different needs.
For example, U.S. Pat. No. 4,481,080 shows a series of printouts separated by baffles for equalizing the residence times of large and small particles. It has been discovered that such solutions are either unnecessarily complex or are unnecessary altogether. It is another aspect of the present invention to provide antimicrobial chemistry as well as devices useful in water recovery and treatment methods, which avoid such deficiencies and solve the needs presented by gross levels of contaminants and other organic matter in process waters.
In several of the above referenced patents their efforts have been directed at chilled water reuse claiming significant savings in BTU requirements. The devices employed have focused upon the recovery, treatment and reuse of the USDA required 0.5 gallon per bird overflow. While the technical approaches may differ from invention to invention, they share the common disadvantages that the source of their water (i.e., bird chiller water) contains a significant and high quantity of organic contaminants as compared to the sources that are identified by the invention herein, and the volumes available for recovery are limited strictly to the USDA mandated 0.5 gallon per bird limitation. It is yet another object of the present invention to avoid the disadvantages associated with such prior art approaches.
The chiller in a poultry slaughter process is used to lower the carcass temperature of slaughtered birds and to introduce antimicrobial agents for the purpose of reducing pathogens both in the chiller water and on the poultry carcasses. The industry standard antimicrobial treatment of poultry chiller water is free chlorine usually delivered in the form of sodium hypochlorite (chlorine bleach). Unfortunately, the use of free chlorine in prior art methods does not reduce pathogens to the desired levels and creates environmental and workplace hazards including hazardous off-gassing within the plant.
The poultry chiller is a large communal bath where fresh carcasses are constantly being added while chilled carcasses are removed. Depending upon the particular plant, carcasses may remain in the chiller for 1-6 hours. There can be hundreds of carcasses in the chiller at any point in time. Unfortunately, the potential for cross contamination of carcasses in this communal bath is very high. In an attempt to control the concentration (load) of organic material in the chiller, fresh makeup water is added which causes the chiller to overflow in an effort to eliminate contaminants. However, the organic loading of water in a typical chiller remains very high in spite of the added water. For example, the chemical oxygen demand (COD) of water in a typical chiller will often range from 1,000-2,000 parts per million. The challenge of treating this organic load within the water is very difficult and unmet with prior art disinfectants.
USDA FSIS allows the addition of chlorine at levels up to 50 ppm in chiller make-up water. A chlorine demand of 1,000-2,000 ppm cannot be overcome by 50 ppm of free chlorine in the make-up water. Experiments by USDA Western Region ARS concluded that free chlorine residual could not be established in a chiller even by adding up to 400 ppm of free chlorine.
The most commonly used prior art disinfectants in a food processing plant are highly reactive oxidizing agents. One way of predicting the efficacy of certain disinfectants is by the rapidity with which they can oxidize other substances. Greater oxidation speeds often cause higher microbial kills. Ozone and chlorine can oxidize very quickly and are widely used as disinfectants. Unfortunately, the very characteristic that normally makes highly reactive oxidants effective disinfectants in drinking water minimizes their effectiveness in the environment of a poultry chiller or other process water environment having high organic load. The demand for chlorine in chiller water is measured in thousands of parts per million. Being highly reactive, free chlorine will rapidly oxidize, bleach or combine with any component of the chlorine demand. When chlorine combines with another substance, it ceases to be highly oxidative and loses its ability to bleach.
Because of the virtually inexhaustible demand caused by the organic load within a chiller, when free chlorine is added to the chiller, it remains free and therefore active, for only seconds. Even with relatively high doses of free chlorine, the contact time with chiller microorganisms is so short, that the Concentration-Time (CT) Value always remains low.
Because of the problems with using free chlorine within the food processing environment, a substantial number of compounds have been explored for use as disinfectant in place of chlorine. For example, U.S. Pat. Nos. 5,437,868, 5,314,687 and 5,200,189 to Oakes et al. are directed to peroxyacetic acid type compounds used as antimicrobials. Another attempt to improve disinfectants within the food industry is set forth in U.S. Pat. Nos. 6,545,047 and 6,103,286 to Gutzmann et al. “Treatment of Animal Carcasses” which also relates to peroxyacetic acid. Unfortunately these compounds are most effective at low pH, which can be destructive to food processing equipment. There can also be worker safety issues involved in the handling of such compounds.
Other efforts towards alternative disinfectants have been directed to the use of acidified sodium chlorite as disclosed in U.S. Pat. No. 6,063,425, Kross et al, “Method for Optimizing the Efficacy of Chlorous Acid Disinfecting Sprays for Poultry and other Meats”. Unfortunately, the disinfectant that is produced by combining the raw materials (sodium chlorite and acetic acid) is generated at a very low pH (about 2.5) which can be destructive to food processing equipment. Off-gassing, which can be detrimental to worker health, can also result from the mixing of chlorine and acidified sodium chlorite within the processing plant.
A further disinfectant by Rhodia is directed at using trisodium phosphate (TSP) as disclosed in U.S. Pat. No. 5,882,253, Mostoller, “Apparatus and Method for Cleaning Poultry”. Unfortunately, there are negative environmental impacts from the addition of trisodium phosphate to a plant's wastewater since phosphate is a regulated wastewater pollutant. There have also been reports of negative impacts to the quality of poultry treated with this compound.
Despite these various chemistries, they are unfortunately used only for on-line reprocessing and in a few selected cases also in the chiller. They suffer from the disadvantage of only being able to be used at one or possibly two specific points in the processing line and not throughout the plant. Unfortunately, none of these above disinfectants have been able to replace chlorine throughout the food processing plant.
While biocides that are not highly oxidative may not have the same disinfectant qualities of those that are highly oxidative in pure water, their use within certain environments offers the potential to be far more effective because such biocides are not as readily consumed by the resident chlorine demand. The less chemically reactive biocide thereby remains active and available to reduce the microbiological populations in the chiller or in other process waters having high organic load. Our discovery is that a relatively small dose of a less potent but more persistent biocide resulting in a residual presence throughout the chiller or other organically laden process water will out perform its highly oxidative counterpart in reducing the overall microbial load.
Another area having high organic loading process water within a poultry processing operation is the poultry scalder tank. The scalder tank is one of the very initial steps in the slaughter process and one of the points in which the water is heavily loaded with organic materials. Water in the scalder has an extremely high organic load, high microbial population and high temperature. The scalder is a communal tank holding numerous carcasses at any point in time, which like the chiller provides great potential for cross contamination. The conditions in the scalder (i.e., high organic load and high temperature) cause the rapid consumption of free chlorine, which significantly degrades the disinfection potential of the chlorine.
Research has indicated that aeration and boiling of water, characteristics of normal scalder operations, will not destroy monochloramine. This characteristic of monchloramine allows a pathogen reduction step at scalders that is not appreciably affected by temperature or aeration. It has also been found that monochloramine is more effective than free chlorine for inactivation of biofilm bacteria, as the greater penetrating power of monochloramine more than compensates for its reduced disinfection activity.
Yet another area of high water use within poultry processing and therefore the need for effective disinfection of water is the evisceration line and various wash cabinets on the processing line. These points of treatment within the evisceration line are between the scalder at one end and the chiller at the other end of a typical poultry processing plant. USDA regulations allow poultry processors to recondition used process water to specific treatment standards for reuse. While this reuse water is typically treated to be pathogen free and often has a turbidity level comparable to potable water, the reuse water does have higher levels of soluble organic loading than found in fresh water. Because of this organic loading, any applied free chlorine will be rapidly consumed, precluding the establishment of an active residual disinfectant. Unfortunately, the lack of an active residual disinfectant will enable bacterial regeneration in water storage and distribution systems.
Advantageously, a chloramine residual can be established in recycled water that is rich with organics. This residual can then be used both to reduce the potential for bacterial regeneration and to subsequently help disinfect whatever the recycled water contacts. The inventive method therefore broadens the potential applicability of water reuse systems within poultry processing plants. With chloramine treatment, the quality of disinfected recycled water can be effectively maintained and the water itself can be used as a vehicle to deliver an effective anti-microbial agent. The inventive method therefore enhances the economic viability and effectiveness or water reuse systems within poultry processing and other food processing systems.
The stable active residual provided by monochloramine and its enhanced ability to penetrate bacterial cell walls provides consistent pathogen reduction on equipment used in a poultry processing plant.
It is contemplated within the scope of this invention that chloramination can be universally applicable to the treatment of food processing waters and the manufacture of ice independent from or in conjunction with any or all steps described herein regarding the treatment of process waters for reuse.